1. Field of the Invention
The present invention relates to a method of manufacturing a light-emitting device including a light-emitting diode element (hereinafter, referred to as LED element) or the like, more specifically, to a method of manufacturing a light-emitting device having a high heat-release property, and capable of miniaturization and thinning.
2. Description of the Related Art
An LED element has widely been used for a backlight of a color display, illumination or the like, because the LED element has a long service life and can be miniaturized, has excellent driving characteristics and high light-emitting efficiency, and is capable of emitting bright emission color.
In particular, there is proposed a light-emitting device in which an LED element is directly disposed on a metallic plate having excellent heat-release property and the metallic plate is used as an output electrode (for reference, see Japanese Patent Application Publication Nos. 2001-326295, 2008-186946 and 2001-210743).
Conventional light-emitting devices using metallic plates as output electrodes are described.
FIG. 6 is a sectional view showing a conventional light-emitting device as disclosed in Japanese Patent Application Publication No. 2001-326295. In FIG. 6, the light-emitting device 100 has a structure including a first metallic frame 102 on which an LED element 101 is mounted, a second metallic frame 103 for an electrode to which at least one of p-n element electrodes of the LED element 101 is electrically connected by a wire 106, and a sealing resin 107 to seal the mounted LED element 1. The first metallic frame 102 and the second metallic frame 103 are integrally connected by the sealing resin 107.
FIGS. 7, 8 and 9 illustrate a conventional light-emitting device as disclosed in Japanese Patent Application Publication No. 2008-186946.
FIG. 7 is a plan view of a lead frame 210, FIG. 8 is a plan view of a lead frame 210 on which LED elements 1 are mounted, and FIGS. 9A to 9C are sectional views of a light-emitting device 200. The drawings show a configuration of the light-emitting device in a simplified state within a required scope.
In FIG. 7, the lead frame 210 is provided with first metallic plates 212 and second metallic plates 213 formed through a process for punching the lead frame 210, each of the first metallic plates 212 having a connecting electrode 214 formed at one side and each of the second metallic plates 213 having a connecting electrode 214 formed at one side. Note that FIG. 7 shows a structure to manufacture a plurality of light-emitting devices 200 simultaneously. The lead frame 210 includes a plurality of setting members necessary to assemble the light-emitting device. The setting members comprise the first metallic plates 212, the second metallic plates 213 and connecting frames 215 formed between the first metallic plates 212 and between the second metallic plates 213, respectively.
FIG. 8 is a plan view showing a state where the LED elements 1 are mounted on the lead frame 210 as shown in FIG. 7. After each of the LED elements 1 is mounted on an upper surface of each of the first metallic plates 212, the p-electrode and the n-electrode of each of the LED elements 1 are electrically connected to the first metallic plate 212 and the second metallic plate 213 through wires 6, respectively, and a portion surrounded by a dotted line is sealed by the sealing resin 207. Meanwhile, a dashed line surrounding each of the LED elements 1 indicates a sealing resin 207a configuring a light-emitting device 200 (mentioned below).
FIGS. 9A to 9C are sectional views showing processes of manufacturing the light-emitting device 200. More specifically, FIG. 9A is a sectional view taken along the line A-A in FIG. 8 showing the sealing resins 207a shown by the dashed line, FIG. 9B is a sectional view showing the connecting electrodes 214 of the first metallic plate 212 and the second metallic plate 213, which are bent downward and folded on a lower surface of the lead frame to act as outer electrodes, and FIG. 9C is a side view showing the light-emitting device 200, in which the LED elements 1, the first and second metallic plates 212 and 213 (shown by a dotted line) are provided. A part of the lead frame 210 cut in a cutting and separating process is exposed from a side surface of the light-emitting device as a cut surface 216.
A conventional light-emitting device disclosed in Japanese Patent Application Publication No. 2001-210743 is described with reference to FIGS. 10A and 10B, and 11A to 11C. FIG. 10A is a plan view of a metallic base 310, and FIG. 10B is a sectional view taken along the line B-B in FIG. 10A showing the metallic base 310. Island-shaped convex portions 310a separated in a grid pattern by concave portions 310b are arranged on the metallic base 310 in a matrix.
FIGS. 11A to 11C are sectional views showing processes of manufacturing a light-emitting device 300. FIG. 11A illustrates a state where one LED element 1 is mounted on three convex portions 310a, the LED element 1 is fixed to the metallic base 310 by a mount material 320 such as a silver paste or the like, and electrically connected to circumferential convex portions 310a by wires 6. In this state, the entire convex portions 310a are in an electrical short-circuit.
FIG. 11B illustrates a state where the LED element 1 mounted on the metallic base 310 is sealed by a sealing resin 307. From this state, a bottom portion 310c of the metallic base 310 is cut along a line C to achieve a state where the bottom portion 310c is cut, as shown in FIG. 11C. That is, the convex portions 310a1 on which the LED element 1 is mounted and the convex portions 310a2 to which the wires are connected are electrically separated, whereby the convex portions 310a2 function as outer electrodes.
By the way, in the proposal shown in Japanese Patent Application Publication No. 2001-326295, the first metallic plate 102 on which the LED element 101 is mounted, and the second metallic plate 103 to which the element electrode of the LED element 101 is electrically connected by the wire 106 are connected and integrated by the sealing resin 107. Here, a transparent or light-transmitting silicone resin is typically used for the sealing resin 107. However, the first metallic plate 102 and the second metallic plate 103 cannot be connected securely with the strength of the silicone resin, and since it is necessary to provide steps 102a and 103a on lower surfaces of the first and second metallic plates 102 and 103 and reinforce the connection thereof with the sealing resin 107, as shown in FIG. 6, there is a problem that the first metallic frame 102 and the second metallic frame 103 have a complicated shape.
In the proposal shown in Japanese Patent Application Publication No. 2008-186946, because it is necessary to cut a complex of metal and resin after the lead frame 210 as a metallic frame is molded by the sealing resin 207, a method of cutting the light-emitting device 200 is limited to a practical press work. In addition, because a part of the lead frame 210 is exposed from a side surface of the light-emitting device 200 as cutting surfaces 216, as shown in FIG. 9C, water enters an inside of the light-emitting device 200 through the exposed part, hence there is a possibility that characteristics of the light-emitting device 200 deteriorate.
In the proposal shown in Japanese Patent Application Publication No. 2001-210743, in the complete process of the light-emitting device 300, because a process of cutting the bottom portion 310c of the metallic base 310 is required, there is a problem that the manufacturing process is unsuitable for mass production.